System for Extending the Life of Thin Walled Tubing and Austempered Weld Stress Relieved Thin Walled Tubing

ABSTRACT

The present invention is directed to a method of extending the life of thin walled tubing by austempering the tubing in a controlled continuous run process involving heating, quenching, and cooling the tubing pursuant to predetermined process parameters. The invention is also directed to a process for austempering tubing having a welded seam and for relieving residual stress in the weld. The invention is further directed to the product of the above processes as well as an austempered weld stress relieved thin walled tubing and such tubing in combination with other apparatus with which it is suitable for use in the production of hydrocarbons.

RELATION TO OTHER APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/943,575, filed Sep. 17, 2004 and still pending.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The present invention is directed to a method of extending the life ofthin walled tubing by austempering the tubing in a controlled processinvolving heating, quenching, and cooling the tubing pursuant topredetermined process parameters. The invention is also directed to aprocess for austempering tubing having a welded seam and for relievingresidual stress in the weld. The invention is further directed to theproduct of the above processes as well as an austempered weld stressrelieved thin walled tubing and such tubing in combination with otherapparatus with which it is suitable for use in the production ofhydrocarbons.

2. Description of the Prior Art

As each instance tubing is rolled on or off a coil tubing reel, it ispermanently elongated. The elongation accumulates until exhausted andthe tubing breaks. Hence, elongation is a significant property of thetubing material.

The second significant property of tubing material is strength orhardness. This quality resists dilation stresses of pressure and tensionstresses of deployments in deep wells.

A characteristic of steel is decreasing elongation with increasinghardness. Metallurgically, an ideal coil tubing is a paradox: hard forstrength in deep or high pressure wells, ductile for repetitive reeling.

Present technology coil tubing steels have a martensitic structure.Martensite has unfavorable hardness versus elongation trade-off. On theother hand, austempered steels have a bainitic structure. Bainiticstructured steels are not only hard, but also retain commendableelongation.

Austempering of steel is known in the prior art; however, it istypically accomplished in a non-continuous batch process which isunsuitable for coil tubing milling.

Represented by FIG. 1 is the current technology to continuously millsteel tubing: metal strip is introduced to a tube formation device, theseam welded and scarfed, and the formed tubular annealed, e.g., byheating. The tubing is chilled by a cooling apparatus and then travelsthrough additional formation devices, e.g., sizing rolls. The tubularmay then be heated and cooled again and taken up, e.g., on a reel. Bywelding the butts of the strip stock at the front end of the process,very long lengths of tubing can be milled.

In the continuous tube milling process, the sizing operation in FIG. 1work-hardens the tubing increasing the strength. The thermal processesdepicted in FIG. 1 are either palliatives for problems caused bywelding, or to soften tubing to the desired grade after work-hardening.The thermal processes used in present tubing milling technology do notharden the tube.

SUMMARY OF THE INVENTION

The present inventions are directed toward an apparatus and methodsuseful for increasing the strength of the tubing while maintaining theelongation of thin walled tubing by austempering the thin walled tubing.The present invention is further directed toward a method foraustempering thin walled tubing comprising a welded seam and for stressrelieving the welded seam. The present invention is also directed towarda product produced by the methods and/or processes described above. Thepresent invention is also directed toward a thin walled austemperedtubing comprising a stress relieved welded seam.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic overview of a prior art system.

FIGS. 2 and 2 a are schematic overviews of an exemplary apparatus forpracticing the present inventions' methods.

FIG. 3 is a view in partial perspective of a section of austemperedtubing.

FIG. 4 is a schematic view of an exemplary deployment of austemperedtubing in a well.

FIG. 5 is a block diagram of a first method of the present invention.

FIG. 6 is a block diagram of a second method of the present invention.

FIG. 7 is a block diagram of a third method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 2, exemplary apparatus 10 for austempering thinwalled tubing according to the methods of the present inventionscomprises heater 20, low temperature reservoir 30, and cooler 40.Apparatus 10 is adapted to be used with continuous runs of tubing 12while practicing the methods of the present invention. As used herein, acontinuous run is one which processes a length of around 200 feet ormore in a single processing procedure.

Metallic tubing 12 has a wall thickness of less than 0.25 inches,preferably around 0.120 inches. In an embodiment, metallic tubing 12comprises a steel alloy with a carbon content greater than or equal to0.25 and less than or equal to 0.45 and may comprise 4130 alloy steel.Metallic tubing 12 may be supplied from source 15 of a substantiallycontinuous supply of metal, e.g. a rolled strip, and formed into atubular at tube former 90. Seams created by tube formation may be weldedat seam welder 91 and the formed seam scarfed at scarfer 92.

Heater 20 is adapted to accept a section of metallic tubing 12 and heatthe section to a high temperature in the range of 1300-1600° F. Heater20 may comprise an induction heater and/or a flame or the like, or acombination thereof. Heater 20, e.g. an induction heater, may be locatedproximate to or within low temperature reservoir 30.

Low temperature reservoir 30 is adapted to accept a moving section ofmetallic tubing 12 as part of a continuous run process and to reduce thetemperature of the section of metallic tubing to a first low temperaturein the range of 500-1000° F. in a time period of less than 3 seconds.Low temperature reservoir 30 as used for quenching may comprise a moltensalt bath. Moving may be accomplished by numerous equivalent meansincluding by using rollers.

Cooler 40 is adapted to cool a section of metallic tubing 12 to a secondlow temperature below 100° F. Cooling may be accomplished by numerousequivalent means including by forced convection. Additional coolers maybe present, e.g. water cooler 93, as is practiced in the art.

Additional processing may occur after the second cooling. For example,austempered metallic tubing 12 may be sized at sizing rollers 94 andcooled further by coolers 96 and 97.

Austempered metallic tubing 12 may then be taken up, e.g. at takeup reel17.

Austempered thin walled welded tube 12 may be coiled on a reel, e.g.,takeup reel 17, which may be further mounted on ship 16 (FIG. 2 a).

Referring to FIG. 3, austempered thin walled welded tube 12 may comprisefirst end region 12 a adapted to be attached to device 19, e.g. a motor,an overshoot jar, an intensifier, a landing nipple, a plug catcher, acasing scraper, a snake pin, a downhole tool, a valve, or the like.Austempered thin walled welded tube 12 may further comprise second endregion 12 b opposite first end region 12 a which may be adapted to befurther connected to device 18, e.g. a pump.

Austempered, thin walled, and stress relieved welded tubing 12 may beproduced by any of the exemplary methods described herein. Moreover,thin walled welded tube 12 produced by any of the exemplary methodsdescribed herein may comprise an austempered cylindrical body created aspart of the continuous run processes of those methods where theaustempered cylindrical body comprises first seam edge 12 c, second seamedge 12 d, and a wall having a thickness of less than 0.25 inches. Thinwalled welded tube 12 may further comprise stress relieved welded seam12 e joining the first and second seam edges.

Referring now to FIG. 4, in an exemplary embodiment thin walled weldedtube 12 is unspooled from takeup reel 17. One end of thin walled weldedtube 12 is connected to pump 18 and the other end deployed through wellcasing 90 and/or production tubing 91, terminating in tool 19.

In the operation of exemplary embodiments, referring now to FIG. 5, in afirst exemplary method for austempering thin walled tubing, a section ofmetallic tubing 12 (FIG. 2 a) is heated to a high temperature in therange of 1300-1600° F. in heater 20 (FIG. 2 a). The section of metallictubing 12 has a wall thickness of less than 0.25 inches, preferablyaround 0.120 inches.

After being heated, the section of heated metallic tubing 12 (FIG. 2 a)is moved from heater 20 (FIG. 2 a) to low temperature reservoir 30 (FIG.2 a) as part of a continuous run process. While in low temperaturereservoir 30, the section of metallic tubing 12 is quenched to reducethe temperature of the section of metallic tubing 12 to a first lowtemperature in the range of 500-1000° F. in a time period of less than 3seconds. Processing the section of metallic tubing 12 may comprise atime-temperature-transformation curve where the start of conversion toaustentite-ferrite is at least 0.75 seconds after quenching in lowtemperature reservoir 30.

The section of metallic tubing 12 (FIG. 2 a) is allowed to transform tobainite and then moved out of low temperature reservoir 30 (FIG. 2 a) aspart of the continuous run process and cooled to a second lowtemperature below around 100° F. Cooling may be by forced convection,e.g. at cooler 40 (FIG. 2 a).

In a second exemplary method, referring to FIG. 6, a further exemplarymethod for austempering thin walled coiled tubing 12 (FIG. 2 a)comprises extending a section of thin walled metallic tubing 12 having awall thickness of less than 0.25 inches from a coil mounted about reel15 (FIG. 2 a) into heater 20 (FIG. 2 a) as part of a continuous runprocess. The section of metallic tubing 12 is heated to a hightemperature in the range of 1300-1600° F. in heater 20 and then movedfrom heater 20 to low temperature reservoir 30 (FIG. 2 a) as part of thecontinuous run process. In low temperature reservoir 30, the section ofmetallic tubing 12 is quenched in low temperature reservoir 30 to reducethe temperature of the section of metallic tubing 12 to a first lowtemperature in the range of 500-1000° F. in a time period of less thanaround 3 seconds.

The section of metallic tubing 12 (FIG. 2 a) is allowed to transform tobainite and then the section of metallic tubing 12 transformed intobainite is moved out of low temperature reservoir 30 (FIG. 2 a) as partof the continuous run process and cooled to a second low temperaturebelow around 100° F., e.g. at cooler 40 (FIG. 2 a).

After it reaches the second low temperature, the section of metallictubing may be coiled, e.g. about reel 17 (FIG. 2 a).

In a third exemplary method, referring now to FIG. 7, a section of thinwalled metallic tubing 12 (FIG. 2 a) having a welded seam and a wallthickness of less than 0.25 inches is extended from a coil mounted aboutreel 15 (FIG. 2 a) into heater 20 (FIG. 2 a) as part of a continuous runprocess. The section of metallic tubing 12 is heated to a hightemperature in the range of 1300-1600° F. in heater 20 (FIG. 2 a) andthen moved from heater 20 to low temperature reservoir 30 (FIG. 2 a) aspart of the continuous run process. In low temperature reservoir 30, thesection of metallic tubing 12 is quenched to reduce the temperature ofthe section of metallic tubing 12 to a first low temperature in therange of 500-1000° F. in a time period of less than around 3 seconds.

The section of metallic tubing 12 (FIG. 2 a) is then allowed totransform to bainite. The section of metallic tubing 12 transformed tobainite is then moved out of low temperature reservoir 30 (FIG. 2 a) aspart of the continuous run process cooled to a second low temperaturebelow around 100° F., e.g. at cooler 40 (FIG. 2 a).

The foregoing disclosure and description of the inventions areillustrative and explanatory. Various changes in the size, shape, andmaterials, as well as in the details of the illustrative constructionand/or a illustrative method may be made without departing from thespirit of the invention.

1. An apparatus for austempering a continuous run of thin walled tubing,comprising: a. a heater adapted to heat a section of continuous runmetallic tubing to a high temperature in excess of around 1300° F.; anon-water based low temperature reservoir operatively in communicationwith the heater and adapted to accept a heated section of the metallictubing from the heater and cool the received heated section of themetallic tubing to a first cooled temperature; and a first cooleroperatively in communication with the non-water based low temperaturereservoir and adapted to accept the cooled section of metallic tubingfrom the non-water based low temperature reservoir and cool the sectionof metallic tubing to a second cooled temperature below 100° F.
 2. Theapparatus of claim 1, wherein the heater is configured to accept asection of metallic tubing that has a wall thickness of less than 0.25inches.
 3. The apparatus of claim 1, wherein the high temperature is inthe range of around 1300 to around 1600° F.
 4. The apparatus of claim 1,wherein the heater comprises at least one of (i) an induction heater or(ii) a flame.
 5. The apparatus of claim 1, wherein the heater is locatedat least one of (i) proximate the low temperature reservoir, (ii)partially disposed within the low temperature reservoir, or (iii)totally disposed within the low temperature reservoir.
 6. The apparatusof claim 1, wherein the low temperature reservoir is a molten salt bath.7. The apparatus of claim 1, wherein the non-water based low temperaturereservoir is adapted to reduce the temperature of the moving section ofthe metallic tubing as part of a continuous run process to a first lowtemperature in the range of 500-1000° F.
 8. The apparatus of claim 1,wherein non-water based low temperature reservoir is adapted to reducethe temperature in a time period of less than 3 seconds.
 9. Theapparatus of claim 1, where the first cooler is a forced convectioncooler.
 10. The apparatus of claim 1, further comprising a plurality ofrollers disposed intermediate the heater, the non-water low temperaturereservoir, and the first cooler.
 11. The apparatus of claim 1, furthercomprising a second cooler adapted to receive the moving section of themetallic tubing from the first cooler.
 12. The apparatus of claim 1,further comprising a take up reel adapted to take up a cooled movingsection of the metallic tubing.